Need Ideas for home automation project! (Auto switch off)

I am thinking of controlling my home appliances(fans)/lightings using a remote/computer/microcontroller. My main objective is power saving. Like as soon as someone leaves a room the lights & fans should turn off automatically. For this I have thought of 2 ideas.

2. Checking whether someone has entered or left the room using laser/IR beam at the door(on the door frame). <<( But I dont know how this can be done as I need to exactly detect if person has gone in the room or come out of the room. Probably this can be done using two beams or one beam & two detectors. ) Also what if more number of persons go in the room.

Can someone please give me idea about this. Also tell me if there can be another technique for this?? :idea:

Other wise use the reflective properties of IR which is used in object avoidance , this sensor circuit can be built in 30 - 40 bucks, u will need two of these , so going in and out can be tracked on how these two activate.

But nothing would beat a PIR sweep of the room and compared to a fixed match to detect if some human is in there .

lol.. swallowing wouldnt do much good.. maximum 12-14 hrs of tracking.. and then ...

but yeah some sort of a wristband wouldnt look very shabby.. wristbands are the in things I guess.. and moreover.. I want to track the movements of the people who live in the house unless I live in an arts gallery or museum where there are a lot of unknowns or new people coming in everyday..

Anyways.. PIR sounded tougher than RFID..ohh and!! the first such system to be documented and commercialized was based on RFID but the guy got the chip/implant embedded under his skin Dr. Kevin Warwick remember??